1. Field of the Invention
The invention relates to a rotating data transmission system for transmission of data between a rotating part and a stationary part, in particular between a rotating part and a stationary part of a computer tomograph, and also to a method for transmitting data via a rotating data transmission device.
2. Description of the Related Art
With rotating units such as radar installations or also computer tomographs, and also with linearly movable units such as crane and conveyor units, it is necessary to transmit electrical signals or energy between units that are movable relative to each other. For this, it is usual to provide a conductor structure in a first unit and a corresponding tap in a second unit. In the following explanations, the term “conductor arrangement” refers to all conceivable forms of conductor structures which are suitable for conducting electrical signals. This applies also to known contacting slide tracks or slip rings. Of substantial importance to transmission by means of rotating data transmission devices or linear “sliding conductors” which also may be designed to be non-contacting, is the short distance of transmission between the units that are movable relative to each other. Thus, optionally a signal may be coupled-out conductively or without contact in a near-field of the conductor arrangements.
A device for transmitting data in computer tomographs is known from U.S. Pat. No. 6,433,631. A transmission signal is applied to a strip conductor line in a rotating part. A tap is provided on the stationary part, which is guided along at a short distance of an order of magnitude of about 1 mm from the strip conductor line. With computer tomographs, the length of the strip conductor line is of an order of magnitude of about 5 meters. At data transmission rates of several tens of gigabits per second, signals must therefore be transmitted with a bandwidth of several gigahertz along a conductor system having a length of about 5 meters. Distortions of the signal arise as a result of frequency-dependent attenuation and dispersion. The signal from the data source (for example a data acquisition system) is supplied via a light-waveguide to the data transmission system. Thus, frequency dependent losses and dispersion will already arise in this light-waveguide. This leads to a deterioration of the input signal of the rotating data transmission system and therefore to a further deterioration of the total output signal.
For improvement of the signals from the optical data path, the application of clock recovery circuits is suggested in U.S. Pat. No. 6,862,299. However, these circuits have the disadvantage that they are usable only to a limited extent particularly at high dispersions.